Bill and others:
The research report on iris and nematodes you asked about was published
in the Journal of Environmental Horticulture, 15(2):108-110. June 1997.
The report was written by Stanton A. Gill and Michael J. Raupp, U. of
Maryland. I'm going to try and synopsize their research and some other
information I'm gathering, but if anyone wants a copy of the actual
report please email me privately (email@example.com) and I will be happy to
mail you a copy.